Folie 1 - RIEGL Laser Measurement Systems
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Multi-wavelength airborne laser scanning ILMF 2011, New Orleans Dr. Andreas Ullrich CTO, RIEGL LMS GmbH introduction: components of ALS systems full waveform analysis vs. online waveform processing primary and secondary ALS data products discussion multi-spectral, hyper-spectral, multi-wavelength selection criteria for laser wavelength availability of laser sources target properties signal attenuation, background radiation laser safety classification of multi-wavelength data / systems conclusions contents RIEGL VQ-580 RIEGL VQ-820-G RiACQUIRE RIEGL LMS-Q680i RiPROCESS IMU & GPS RIEGL DR-680 Flight Guidance components of ALS systems Q-560/Q-680i RIEGL VQ-580 RIEGL VQ-820-G A dev A W R R Full Waveform analysis range: R [m] amplitude: A [LSB and linearized] echo width: W [ns] On-Line Waveform Processing range: R [m] calibrated amplitude: A [dB] calibrated reflectance: r [dB] pulse shape deviation: dev [1] state-of-the-art echo waveform digitizing systems RIEGL LMS-Q680i, wavelength 1550 nm dry conditions wet snow primary data: point cloud RIEGL VQ-580 wavelength 1064 nm pulse amplitude reflectance in dB shape above deviation detection white from threshold diffusely expected reflecting pulse target shape primary data: point cloud 1064 nm 1550 nm visible 532 nm visible 532 nm 1064 nm 1550 nm images at different wavelengths Laser Radar Cross Section (LRCS) cross section in [m²] area-normalized cross section values in [m²m-2] or [dB] by laser footprint area: by illuminated object area: 0 lim 4R 2 R E s Es Ei Ai d 2 actual geometric crosssection of target interacting with laser beam 0 Alf reflectance directivity of backscattered reflection Ai Radiometric calibration of small-footprint airborne laser scanner measurements: Basic physical concepts, Wagner, W., ISPRS Journal of Photogrammetry and Remote Sensing, 65, 2010. radiometric calibration radiometric calibration 400 nm 800 nm 1200 nm 1600 nm multispectral imaging hyperspectral imaging multiwavelength lidar hyperspectral lidar 532 nm 905 nm 1064 nm 1550 nm supercontinuum laser (500 nm – 2400 nm) array of receiver channels and ROIC multispectral/hyperspectral imaging vs. multi-wavelength ALS pulsed time-of-flight laser ranging: best performance wrt maximum range, measurement speed, ranging precision and accuracy selection of wavelength availability of suitable laser and detector reflectance of objects attenuation of atmosphere and background radiation laser safety laser requirements short pulse width (multi-target resolution, high precision) high peak power (maximum range) good beam quality (beam divergence, spatial resolution) high pulse repetition rate (point density) narrow spectral width (background rejection) detector requirements high bandwidth (corresponds to pulse width) high sensitivity (maximum range) low noise (high precision) wavelength selection criteria for ALS sensors 200 400 600 800 1000 UV 1400 1600 1800 2000 INFRARED diode 905 nm solid state fiber 1200 355 nm 532 nm 1064 nm 532 nm 1064 nm 1550 nm 2050 nm diode lasers, 905 nm solid state lasers (fundamental wavelength), Nd:YAG, 1064 nm solid state lasers (harmonics), Nd:YAG, 532 nm, (355 nm) fiber lasers, Er-doped, 1.55 µm fiber lasers, Yt-doped, 1.06 µm fiber lasers, Ho-doped, 2.05 µm frequency-doubled fiber lasers, 532 nm suitable laser sources 532 nm relative reflectance [%] 905 nm 1064 nm 1550 nm wavelength [µm] target reflectance versus wavelength solar spectral irradiance at zenith sun angle 60° at sea level 1400 corresponds to spectrum of sun light solar irradiance [W/m²µm] 1200 532 nm absorption due to ozone (O3) , water vapor (H2O), oxygen (O2), carbon dioxide (C02) 1000 800 600 1064 nm 905 nm 400 1550 nm 200 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 wavelength [µm] background radiation versus wavelength transmittance [%] transmittance of 1000 feet horizontal air path (sea level) 1550 nm 905 nm 1064 nm 532 nm atmospheric transmission 20 km, one way visibility 23 km, 10 km, 5 km wavelength [µm] atmospheric attenuation versus wavelength absorption coefficient of clear seawater ultraviolet visible attenuation at depth 10 m infrared 10 000 attenuation at depth 0.1 m attenuation at depth 1 mm 1 000 100 dB 100 absorption coefficient [cm-1] 50 dB 10 dB 10 1 100 dB 53 dB 0.1 10 dB 0.1 dB 0.01 dB 0.01 100 dB 1 dB 0.001 10 dB 0.1 dB 3.8 dB 0.038 dB 1 dB 0.0001 0.1 0.2 0.4 0.6 0.8 1.0 wavelength [µm] 2.0 4.0 1 dB 0.53 dB 0.01 dB 6.0 8.0 10 attenuation in water versus wavelength MPE: maximum permissible exposure parameter: exposure duration / pulse width 1550 nm 1064 nm 905 nm 532 nm 355 nm laser safety considerations EN60825 class 1 21CFR1040.10 class I class 1M - class 2 class II class 2M - class 3R class IIIA class 3B class IIIB class 4 class IV RIEGL LMSQ680i RIEGL RIEGL VQ-580 VQ-820-G @ 50kHz @ 100kHz @ 80kHz 1.5m 15m 0m NOHD NOHD, NOHD eNOHD eNOHD 80m eNOHD 10m 105m 500m 1600m 1600m 1600m 2000m 2000m 2000m max. range @ reflectance 20% Range [m] Laser Safety Standards max. range @ reflectance 80% NOHD (nominal ocular hazard distance): distance beyond which exposure becomes less than maximum permissible exposure (MPE) extended NOHD: includes the possibility of optically-aided viewing Laser Classes / NOHD / ENOHD description same area common platform common scanner same IFOV data set from two different campaigns X data from several laser scanners on same platform X X several LIDARs sharing the same scanner X X X co-axial beams having thus the same instantaneous field-of-view X X X X additionally pulses of LIDARs are synchonized X X X X synchron ized pulses X increasing sensor/system complexity increasing flexibility classification of multi-wavelength ALS select scanner model (wavelength) according to target characteristics, mission requirements, laser safety requirements, ... wide variety of applications covered by eye-safe 1550 nm ALS scanners (e.g., RIEGL LMS-680i and RIEGL VQ-480) for special applications, e.g., forest health investigations integrate two or more scanners with different wavelength on a single platform providing flexible “multi-wavelength” system (e.g., RIEGL VQ-480 at 1550 nm and RIEGL VQ-580 at 1064 nm) for hydrography, ad 532 nm LIDAR regardless of wavelength: echo-digitizing pulsed time-of-flight systems provide utmost accuracy, multi-target resolution and calibrated (calibratable) amplitudes and target’s cross-section conclusions
